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          <div class="quiz-container">
            <div class="quiz-header">
              <h1>什么是循环展开？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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      <script>
        const quizData = [
  {
    "question": "根据文档，循环展开（Loop Unrolling）这项编译器优化技术的核心目标是什么？",
    "options": [
      "通过代码复用减少最终程序的体积",
      "简化复杂循环的逻辑，以提高代码可读性",
      "减少循环控制开销和分支跳转，以提升程序执行效率",
      "在程序运行时动态调整循环次数以适应不同硬件"
    ],
    "correctAnswerIndex": 2,
    "explanation": "循环展开的核心思想是通过将循环体代码复制多次来减少总的循环迭代次数。这样做的主要好处是减少了每次迭代都需要的循环控制开销（如索引递增和条件判断）以及分支跳转指令，从而提高了CPU指令流水线的效率和整体性能。",
    "source": "文档中「循环展开的定义」部分",
    "hint": "其核心思想是在编译时或手动将循环体的多次执行合并成一次，甚至完全展开，从而降低循环的开销。"
  },
  {
    "question": "在Java生态系统中，循环展开优化通常是由哪个组件负责执行的？",
    "options": [
      "由Java开发者在编写高性能代码时手动实现",
      "由javac编译器在将.java文件编译为.class字节码时完成",
      "由JVM的即时编译器（JIT）在运行时对频繁执行的“热点代码”进行优化",
      "由Java的垃圾收集器（GC）在整理内存碎片时附带执行"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，在Java中，循环展开主要由JVM的即时编译器（JIT）在程序运行时自动完成。JIT会识别并优化那些被频繁执行的“热点代码”，循环展开是其重要的优化手段之一，而开发者通常不需要手动干预。",
    "source": "文档中「循环展开在Java中的应用」部分的「JVM中的循环展开优化」小节",
    "hint": "在Java中，循环展开主要由JVM的即时编译器（JIT）来执行。JIT编译器在运行时分析字节码，将热点代码...编译为本地机器码，并应用各种优化技术..."
  },
  {
    "question": "尽管循环展开能提升性能，但它最主要的缺点或代价是什么？",
    "options": [
      "代码膨胀，可能导致指令缓存压力增大，反而降低性能",
      "显著增加了垃圾收集（GC）的暂停时间",
      "导致算法的时间复杂度从O(n)变为O(n^2)",
      "使得程序无法在多核处理器上并行执行"
    ],
    "correctAnswerIndex": 0,
    "explanation": "循环展开的主要代价是代码膨胀。因为循环体被复制了多次，导致最终生成的机器码体积增大。这可能会增加指令缓存（Instruction Cache）的压力，如果展开后的代码超出了缓存大小，可能导致缓存未命中率增加，从而抵消了优化带来的性能提升。",
    "source": "文档中「循环展开的优缺点」部分的「缺点」小节",
    "hint": "循环展开会导致代码体积增加...这种膨胀可能导致指令缓存压力增加，甚至可能导致缓存溢出，从而抵消性能优化带来的收益。"
  },
  {
    "question": "根据文档，以下哪项不是循环展开所带来的性能优势？",
    "options": [
      "减少分支预测失败的可能性",
      "提高指令级并行性（ILP）",
      "降低代码的复杂度和维护成本",
      "提高数据局部性，从而提升缓存命中率"
    ],
    "correctAnswerIndex": 2,
    "explanation": "循环展开的主要优势在于性能提升，包括减少分支跳转、提高指令并行性和缓存命中率。然而，它的一个显著缺点是会使代码变得更冗长、复杂，从而降低了代码的可读性和可维护性，增加了维护成本。",
    "source": "文档中「循环展开的优缺点」部分",
    "hint": "手动展开的代码往往比原始代码更加冗长且复杂，这会降低代码的可读性和可维护性。"
  },
  {
    "question": "当循环的迭代总次数不是展开因子（unroll factor）的整数倍时，编译器通常采用什么策略来确保程序的正确性？",
    "options": [
      "在展开的循环体内增加if-else分支来处理剩余的迭代",
      "放弃优化，直接执行原始的、未展开的循环",
      "抛出编译时错误，强制要求迭代次数必须是整数倍",
      "生成一个展开的主循环处理大部分迭代，再额外生成一个简单的“收尾”循环处理剩余部分"
    ],
    "correctAnswerIndex": 3,
    "explanation": "为了同时获得循环展开的性能优势并保证逻辑的正确性，编译器通常会采用一种组合策略：生成一个高度优化的、展开的主循环来处理成块的迭代，然后用一个简单的、未展开的边界循环（或称为“收尾”循环）来处理剩余的、不足一个展开块的迭代。",
    "source": "文档中「循环展开的工作原理」部分的「边界处理」小节",
    "hint": "编译器通常会生成两个循环，一个是完全展开的主循环，另一个是处理剩余未展开部分的边界循环。"
  },
  {
    "question": "文档中提到了“完全展开”和“部分展开”，这两者之间的关键区别在于什么？",
    "options": [
      "完全展开适用于所有循环，而部分展开只适用于迭代次数固定的循环",
      "完全展开彻底消除了循环控制结构，而部分展开只是减少了循环的迭代次数",
      "完全展开由javac编译器执行，而部分展开由JIT编译器执行",
      "部分展开会产生代码膨胀，而完全展开不会"
    ],
    "correctAnswerIndex": 1,
    "explanation": "“完全展开”是指将循环的每一次迭代都展开为独立的指令序列，从而完全消除循环本身（包括初始化、条件判断和递增等控制结构）。而“部分展开”是一种折衷方案，它只将循环体复制几次，从而减少迭代次数和循环开销，但仍然保留了循环结构。这是一个在性能收益和代码大小之间的权衡。",
    "source": "文档中「循环展开的定义」部分的「完全展开与部分展开」小节",
    "hint": "在完全展开中，循环的每一轮都会被展开成单独的代码块，彻底消除循环控制结构。而在部分展开中，仅仅是减少了循环的迭代次数，并没有完全消除循环控制。"
  },
  {
    "question": "循环展开能提高指令级并行性（Instruction-Level Parallelism, ILP），其主要原理是？",
    "options": [
      "通过减少内存访问次数，让CPU有更多时间执行计算指令",
      "展开后的循环体包含更多独立的指令，使得处理器可以在一个时钟周期内执行多条指令",
      "它强制操作系统为程序分配更多的CPU核心",
      "它将复杂的指令分解为多个简单的指令"
    ],
    "correctAnswerIndex": 1,
    "explanation": "现代处理器通常具有超标量架构，可以同时执行多条没有数据依赖的指令。循环展开通过将多个迭代的操作合并在一起，增加了单个“循环体”内的独立指令数量。这为编译器和处理器提供了更大的空间来重新排序和调度指令，从而更充分地利用处理器的并行执行能力，提高ILP。",
    "source": "文档中「循环展开的优缺点」部分的「优点」小节",
    "hint": "展开后的循环体包含更多独立的指令，使得编译器或处理器能够更好地调度这些指令，以实现指令级并行（ILP）。"
  }
];
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  